Dumbbell-loaded folded slot antenna



United States Patent 3,172,112 DUMBBELL-LOADED FOLDED SLOT ANTENNA Elwin W. Seeley, Riverside, Calif., assigner to the United States of America as represented by the Secretary of the Navy Filed May 29, 1961, Ser. No. 113,557 5 Claims. (Cl. 343-767) (Granted under Title 35, U.S. Code (1952), sec. 266) The invention herein described may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

The present invention relates to antenna structures and more particularly to a slot type antenna both for obtaining eliicient radiation over a large range of frequencies and for having a radiation resistance that is easily matched with a given transmission line.

Antennas of the folded slot type and of the dumbbell loaded type are individually known and disclosed in U.S. Patents No. 2,751,589 and No. 2,507,528, respectively. However, the present invention involves a combination of both dumbbell loading and folding of a slot type antenna to result in a single novel antenna having characteristics of both being operable to radiate efficiently over a large range of frequencies and having a radiation resistance that is easily matched with a transmission line. A mere rectangular slot is twice as long as the present loaded folded slot at resonance and has a bandwidth less than the loaded folded slot. The dumbbell loaded slot has a bandwidth much less than that of a load folded slot of the present invention. The present invention is also related to copending application, Serial No. 18,453, filed March 29, 1960, now Patent No. 3,022,505.

It is an object of the invention to provide a single novel slot antenna for radiating efficiently over a large range of frequencies and having a radiation resistance that is easily matched.

Another object of the invention is to provide a novel slot antenna that is both dumbbell loaded and folded, and will operate with a resonant length of less than a quarter Wavelength.

A further object of the invention is to provide a loaded follfcd slot antenna having a half power bandwidth of 60 n.

Other objects and many of the attendant advantages of this invention will become readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

The figure of drawing illustrates an embodiment of the dumbbell-loaded folded antenna of the present invention.

Referring to the drawing, a rectangular slot having large circular holes 12 and 13 at the ends thereof forms a dumbbell shaped slot antenna. The antenna is excited by applying electromagnetic energy, from a feed line, across the rectangular slot 10, called the driven slot, at points 1S and 16. Another slot 18 cut parallel to driven slot 10 and extending between the dumbbell holes 12 and 13 is the folded slot. This dumbbell loaded folded slot can be cut in any metal sheet or in any metal surface having a dielectric support and fed by a transmission line, or 1t can be cut in the metal wall of a waveguide or any transmission line having dielectric supported walls. Also, dielectric material 19 may fill the slots for support in the plane of a metal wall or sheet.

The present loaded folded slot antenna will operate with a resonant length of less than a quarter wavelength, and a half power bandwidth of 60%. An important ad- 3,172,112 Patented Mar. 2, 1965 ICC vantage of this antenna is the selectivity of the resonant radiation resistance which can be varied from 30 to 300 ohms, for example, by changing the width of folded slot 18.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. A slot antenna for radiating efficiently over a large range of frequencies and having an easily matched radiation resistance comprising a substantially fiat metal surface having a rectangular slot cut therein, a circular aperture in said metal surface at each end of said slot having a diameter greater than the width of said slot, a second slot cut in said metal surface parallel to said rectangular slot and extending between said circular apertures, Ifeeding conductors connected to said antenna at feed points on opposite sides of said rectangular slot, the resonant radiation of the antenna being varied by changing the width of said second slot.

2. In a waveguide, a broadband slot antenna comprising an elongated slo-t having circular apertures at each end thereof to form a dumbbell shaped slot, a second slot parallel to said elongated slot, the resonant radiation resistance of the antenna being varied by changing the width of said second slot.

3. A slot lantenna having a resonant length of less than a quarter wavelength and a half power bandwidth of 60% comprising a transmission line having dielectric supported Walls, a rectangular slot cut in a wall of said transmission line, circular apertures at each end of said rectangular slot to form a dumbbell shaped slot, a second slot cut in said transmission line parallel to said rectangular slot and extending between said circular apertures, the resonant radiation of the antenna being varied by changing the width of said second slot.

4. In a metal wall, a slot antenna for radiating efficiently over a large range of frequencies and having an easily matched radiation resistance comprising a driven slot having circular apertures at each end thereof to form a dumbbell shaped slot, a second slot parallel to said driven slot and extending between said circular apertures, dielectric material filling said slot in the plane of the metal wall for supporting the strip of wall formed by the two slots, the resonant radiation of the antenna being Varied by changing the width of said second slot.

5. In a transmission line having a thin metal surface over dielectric material walls, a slot antenna comprising a dumbbell shaped slot formed by removing the thin metal surface from the transmission line wall, a second slot extending between the ends of said dumbbell shaped slot and parallel to the longitudinal axis thereof, the resonant radiation of the antenna being Varied by changing the width of said second slot.

References Cited by the Examiner UNITED STATES PATENTS 3,022,505 2/62 Scharp 343-767 3,031,666 4/62 Butler 343--771 FOREIGN PATENTS 1,012,833 4/52 France.

HERMAN KARL SAALBACH, Primary Examiner.

GEORGE N. WESTBY, Examiner. 

4. IN A METAL WALL, A SLOT ANTENNA FOR RADIATING EFFICIENTLY OVER A LARGE RANGE OF FREQUENCIES AND HAVING AN EASILY MATCHED RADIATION RESISTANCE COMPRISING A DRIVEN SLOT HAVING CIRCULAR APERTURES AT EACH END THEREOF TO FORM A DUMBBELL SHAPED SLOT, A SECOND SLOT PARALLEL TO SAID DRIVEN SLOT AND EXTENDING BETWEEN SAID CIRCULAR APERTURES, DIELECTRIC MATERIAL FILLING SAID SLOT IN THE PLANE OF THE METAL WALL FOR SUPPORTING THE STRIP OF WALL FORMED BY THE TWO SLOTS, THE RESONANT RADIATION OF THE ANTENNA BEING VARIED BY CHANGING THE WIDTH OF SAID SECOND SLOT. 